372 



EMBRYO OF FINALES 



themselves in a plate. By successive division these cells are 

 increased until usually four plates of four cells each are formed 



Fig. 256. Development of the young sporophyte or embryo: 2, diagram 

 of a section of a megasporangium, showing the formation of elongated sus- 

 pensory cells and numerous embryos, e; i, integument; sp, sporangium nearly 

 consumed by the growth of the gametophyte; g, gametophyte, the central 

 portion of it disorganized by growth of embryos, e. 3^, section of a nearly 

 mature embryo; s, suspensor; r, root cap; c, cotyledons; st, stem. 3B, external 

 view of embryo. 



which become surrounded by cell walls save in the case of the 

 lower plate, which is in direct contact with the rich food of the 

 spore (Fig. 255, C-D). This meager growth corresponds to the 



Fig. 257. Sectional view of pine seed: i, hard integument; g, gameto- 

 phyte, often called the endosperm, which has completely consumed the spor- 

 angial tissues. The embryo consists of a root, r, ensheathed in a large root cap 

 cotyledons, c, and stem, s. 



